CN115552270A

CN115552270A - Ferromagnetic frame for magnetic resonance imaging

Info

Publication number: CN115552270A
Application number: CN202080096140.7A
Authority: CN
Inventors: C·胡根; H·A·迪沃恩; 迈克尔·斯蒂芬·普尔
Original assignee: Hepperfina Operation Co ltd
Current assignee: Hepperfina Operation Co ltd
Priority date: 2019-12-10
Filing date: 2020-12-09
Publication date: 2022-12-30
Also published as: WO2021119063A1; US20210173025A1; US20230095957A1; US20210173027A1; US11422213B2; EP4073531A1; US11333727B2

Abstract

For providing B for a magnetic resonance imaging system (100, 700) ₀ A device (200, 300, 600, 900) for magnetic fields. The device (200, 300, 600, 900) comprises at least one permanent B ₀ A magnet (122, 210, 910) and a ferromagnetic frame (220), wherein at least one permanent B ₀ The magnet (122, 210, 910) is used for B to the MRI system (100, 700) ₀ The magnetic field contributes a magnetic field, and the ferromagnetic frame (220) is configured to capture and guide the magnetic field ₀ At least some of the magnetic fields generated by the magnets (122, 210, 910). The ferromagnetic frame (220) includes a first post (222 a, 922) having a first end (223 a) and a second end (223 b), a first multi-prong member (224 a, 924) coupled with the first end (223 a), and a second multi-prong member (223 b) coupled with the second end (223 b)A second multi-pronged member (224B, 924), wherein the first and second multi-pronged members (224 a, 224B, 924) support at least one permanent B ₀ A magnet (122, 210, 910).

Description

Ferromagnetic frame for magnetic resonance imaging

Cross Reference to Related Applications

This application claims priority under section 119 (e) of U.S. code 35 of the U.S. code, U.S. provisional patent application serial No. 62/946,000 entitled "ferromagonetic FRAME FOR MAGNETIC RESONANCE IMAGING" filed on 12, 10, 2019, which is incorporated herein by reference in its entirety.

Background

Magnetic Resonance Imaging (MRI) provides an important imaging modality for many applications and is widely used in clinical and research environments to produce images of the interior of the human body. Generally, MRI is based on detecting Magnetic Resonance (MR) signals, which are electromagnetic waves emitted by atoms in response to changes in state caused by an applied electromagnetic field. For example, nuclear Magnetic Resonance (NMR) techniques involve detecting MR signals emitted from nuclei of excited atoms as nuclear spins of atoms (e.g., atoms in human tissue) in an object being imaged realign or relax. The detected MR signals may be processed to generate images, wherein the images in the context of medical applications allow investigation of internal structures and/or biological processes within the body for diagnostic, therapeutic and/or research purposes.

Disclosure of Invention

Some embodiments relate to an apparatus for providing a B0 magnetic field for a Magnetic Resonance Imaging (MRI) system. The apparatus comprises: at least one permanent B0 magnet that contributes a magnetic field to a B0 magnetic field of the MRI system; and a ferromagnetic frame configured to capture and direct at least some of the magnetic fields generated by the at least one permanent B0 magnet. The frame includes: a first post having a first end and a second end; a first multi-pronged member coupled with the first end; and a second multi-pronged member coupled with the second end, wherein the first and second multi-pronged members support the at least one permanent B0 magnet.

Some embodiments relate to a method, comprising: a patient is imaged using a magnetic resonance imaging system, i.e. an MRI system. The MRI system includes: at least one permanent B0 magnet that contributes a magnetic field to a B0 magnetic field of the MRI system; and a ferromagnetic frame configured to capture and guide at least some of the magnetic fields generated by the at least one permanent B0 magnet. The ferromagnetic frame includes: a first post having a first end and a second end; a first multi-pronged member coupled with the first end; and a second multi-pronged member coupled with the second end, wherein the first and second multi-pronged members support the at least one permanent B0 magnet.

Some embodiments relate to a framework for capturing and guiding at least some of the B0 magnetic fields generated by a Magnetic Resonance Imaging (MRI) system. The frame includes: a ferromagnetic frame configured to capture and guide at least some of the B0 magnetic field generated by at least one permanent B0 magnet. The ferromagnetic frame includes: a first post having a first end and a second end; a first multi-pronged member coupled with the first end; and a second multi-pronged member coupled with the second end, wherein the first and second multi-pronged members support the at least one permanent B0 magnet.

Some embodiments relate to an apparatus for providing a B0 magnetic field for a Magnetic Resonance Imaging (MRI) system. The apparatus comprises: at least one permanent B0 magnet that contributes a magnetic field to a B0 magnetic field of the MRI system; and a ferromagnetic frame configured to capture and guide at least some of the magnetic fields generated by the B0 magnet. The frame includes: a first plate configured to support at least one permanent B0 magnet; and a first post attached to the first plate using a first connection fitting, wherein the first connection fitting comprises: a first connector connecting the first post with the first plate; and a second connector attached to the first connector.

Some embodiments relate to methods and systems for capturing and guiding B generated by a Magnetic Resonance Imaging (MRI) system ₀ A framework of at least some of the magnetic fields. The frame includes at least one permanent B configured to capture and guide the movement of the at least one permanent B ₀ Magnet generated B ₀ A ferromagnetic frame of at least some of the magnetic fields. The ferromagnetic frame includes: a first column comprising a body portion, a first end and a second end, each of the first and second ends comprising a layered junction (layred junction) coupled with the body portion of the first column; and a first plate coupled with the first end of the first post, wherein the first plate supports the at least one permanent B ₀ A magnet.

Drawings

Various aspects and embodiments will be described with reference to the following drawings. It should be understood that the drawings are not necessarily drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing.

Fig. 1 illustrates exemplary components of an example Magnetic Resonance Imaging (MRI) system, in accordance with some embodiments of the technology described herein;

FIG. 2 illustrates a method for providing B for an MRI system, in accordance with some embodiments of the technology described herein ₀ Exemplary embodiments of a device for magnetic fields;

FIG. 3 illustrates an assembly including radial blades for providing B for an MRI system according to some embodiments of the technology described herein ₀ Exemplary embodiments of a device for magnetic fields;

4A-4C illustrate different embodiments of a blade used as part of the example apparatus shown in FIG. 3, in accordance with some embodiments of the technology described herein;

FIG. 5 illustrates a method for providing B for an MRI system, in accordance with some embodiments of the technology described herein ₀ Different embodiments of the apparatus of magnetic fields simulate gradient field decay over time;

fig. 6A-6C illustrate a method for providing B for an MRI system, in accordance with some embodiments of the technology described herein ₀ A map of a device that is magnetic and includes a non-conductive support structure;

FIG. 7 illustrates a portable MRI system including the apparatus of FIG. 3 in accordance with some embodiments of the techniques described herein;

figure 8 illustrates capturing a magnetic resonance image of a patient's head using the portable MRI system of figure 7, in accordance with some embodiments of the techniques described herein;

9A-9D illustrate a fitting including a ferromagnetic connector and a blade for providing B for an MRI system according to some embodiments of the technology described herein ₀ A map of the apparatus of the magnetic field; and

10A-10B illustrate a method for providing B for an MRI system in which a fitting includes a ferromagnetic plate and a connecting fitting, according to some embodiments of the technology described herein ₀ Diagram of a device of magnetic fields.

Detailed Description

Conventional Magnetic Resonance Imaging (MRI) systems are mostly high-field systems, in particular for medical or clinical MRI applications. The general trend in medical imaging has been to produce MRI scanners with increasingly greater field strengths, with the vast majority of clinical MRI scanners operating at 1.5T or 3T, using higher field strengths of 7T and 9T in the research environment. Although clinical systems operating between 0.5T and 1.5T are also generally characterized as "high-field," as used herein, "high-field" generally refers to MRI systems currently used in clinical settings, and more particularly, to main magnetic fields (i.e., B) at or above 1.5T (i.e., B £ T) ₀ Field) MRI systems that operate under. In contrast, despite having a B between 0.2T and about 0.3T ₀ Systems of fields are sometimes characterized as low fields due to an increase in field strength at the high end of the high-field region, but "low field" generally refers to a B of less than or equal to about 0.2T ₀ An MRI system operating under field.

Some low-field MRI systems increase accessibility to the imaging region by employing magnet assemblies having a C-shaped design. Such designs use a C-shaped steel frame to support the magnetic components of the MRI system, with a single column connecting the two halves of the MRI system, with the imaging region located between the two halves. An example of such a C-shaped design is described in U.S. Pat. No. 5, 10,353,030 entitled "Low-Field Magnetic Resonance Imaging Methods and Apparatus", granted at 16/7/2019, which is incorporated herein by reference in its entirety. However, the inventors have recognized that there are benefits (e.g., reduced system weight and/or increased field efficiency) to using a design with additional support.

Accordingly, the inventors have developed a lighter frame than a C-shaped design to support the B of an MRI system ₀ A magnet. In particular, the inventors have developed a bifurcated frame that supports B by reducing the number of legs in comparison to a C-shaped design ₀ The amount of material (e.g., steel) of the magnets reduces the weight of the overall system. In addition, the framework developed by the inventors reduces the conduction of eddy currents in the framework caused by the gradient field, thereby increasing the gradient field efficiency of the MRI system and improving image quality by reducing eddy current-related artifacts.

Another benefit of the bifurcated frame design developed by the inventors is that shimming complexity can be reduced to achieve a desired degree of homogeneity (homogeneity) of the main magnetic field. The asymmetry of the C-shaped design causes B ₀ Asymmetry of the magnetic field, which can be compensated by shimming to provide a suitably uniform B in an imaging zone of the MRI system ₀ A field. The symmetry of the bifurcated frame design developed by the inventors may reduce the extent to which shimming must be performed, thereby simplifying the manufacturing process of the MRI system, which makes the manufacturing process faster and cheaper.

The inventors have also recognized that attaching the blades to the bifurcated frame may enhance the main and gradient magnetic fields of the MRI system. The blades may be sparsely arranged near the gradient coils to provide improved gradient field efficiency during imaging. Additionally, positioning the blade at B ₀ The proximity of the magnet can improve DC field efficiency by directing magnetic flux to the imaging region.

The inventors have developed a method for providing B for an MRI system ₀ A device for a magnetic field. In some embodiments, the device may include at least one permanent B ₀ Magnets (e.g., magnets comprising NdFeB, smCo, alNiCo, feN, and/or other permanent magnetic materials). The at least one permanent B ₀ The magnet can generate a magnetic field to contribute to B ₀ A magnetic field. The apparatus may further comprise a memory configured to store the dataCapture and guide the general expression B ₀ A ferromagnetic frame of at least some of the magnetic fields generated by the magnets. In some embodiments, the frame may include a first post having a first end and a second end, a first multi-pronged (e.g., bifurcated) member coupled with the first end, and a second multi-pronged member coupled with the second end. The first and second multiple prong members may support at least one permanent B ₀ A magnet. In some embodiments, the device may further include a second post having a third end and a fourth end. The third multi-pronged member may be coupled with the third end and the fourth multi-pronged member is coupled with the fourth end.

In some embodiments, the first post, the first multi-prong member, and the second multi-prong member may each be formed of a ferromagnetic material (e.g., steel, silicon steel, etc.). In some embodiments, the second, third, and fourth multi-prong members may each also be formed of a ferromagnetic material. The assembly of the frame formed by ferromagnetic material may guide B ₀ Magnetic flux of a magnet to increase field uniformity and/or increase B within an imaging zone of an MRI system ₀ Magnetic field strength.

In some embodiments, the first multi-prong member can include a stem and two prongs coupled with the stem. The two prongs may be spaced apart from each other by a gap. Each of the two prongs may be curved.

In some embodiments, the first multi-pronged member may be positioned opposite the third multi-pronged member. A gap may exist between the first multi-pronged member and the third multi-pronged member. In some embodiments, the second multi-pronged member may be positioned opposite the fourth multi-pronged member. A gap may exist between the second multi-pronged member and the fourth multi-pronged member. The gap may be an air gap, and the gap may reduce eddy current conduction through the entire ferromagnetic frame.

In some embodiments, at least one permanent B ₀ The magnets are biplane magnets and may include a first concentric permanent magnet ring and a second concentric permanent magnet ring. The first and third multiple fork members may support a first concentric permanent magnet ring and the second and fourth multiple fork members support a second concentric permanent magnet ring.

In some embodiments, the first multi-pronged member and the third multi-pronged member may be coupled with a first non-conductive component (e.g., a plastic component, a fiberglass component, etc.), and the first concentric permanent magnet ring may be arranged on a surface of the first non-conductive component. The second and fourth multiple prong members may be coupled with a second non-conductive component, and the second concentric permanent magnet ring may be arranged on a surface of the second non-conductive component. The first and second non-conductive components may be substantially planar.

In some embodiments, the apparatus may further include a first plurality of ferromagnetic vanes (e.g., fabricated from steel, silicon steel, etc.). The first plurality of ferromagnetic vanes may be coupled with the first or third multi-prong members at an end of each of the first plurality of ferromagnetic vanes. The end of each ferromagnetic leaf of the first plurality of ferromagnetic leaves may be placed within a slot formed in the first multi-prong member or the third multi-prong member. In some embodiments, ferromagnetic vanes of the first plurality of ferromagnetic vanes are arranged to extend radially from a common center. The blades may not contact the common center.

In some embodiments, each ferromagnetic blade may have a constant height and/or width along the length of the ferromagnetic blade. Alternatively, in some embodiments, the height and/or width of each ferromagnetic lobe of the first plurality of ferromagnetic lobes may vary along the length of each ferromagnetic lobe. For example, in some embodiments, the height and/or width of the ferromagnetic vanes may be tapered. In some embodiments, the first plurality of blades includes at least 16 blades and at most 24 blades. Alternatively, in some embodiments, the first plurality of blades comprises 8 to 32 blades.

In some embodiments, the apparatus may include a second plurality of ferromagnetic vanes. The second plurality of ferromagnetic vanes may be coupled with the second or fourth multi-pronged member at an end of each of the second plurality of ferromagnetic vanes. The ends of each ferromagnetic leaf of the second plurality of ferromagnetic leaves may be placed within a slot formed in the second multi-pronged member or the fourth multi-pronged member.

In some embodiments, the first column andthe second columns may be arranged at an angle of 180 deg. such that at least one permanent B is ₀ The magnet is located between the first post and the second post. Alternatively, the first and second columns may be aligned at an angle ranging from 100 ° to 180 °. The first and second columns may be aligned at an angle ranging from 120 ° to 145 °. The first and second columns may be arranged at an angle of 120 °. Reducing the angle between the first and second posts can provide more accessibility to one side of the imaging zone while maintaining most of the advantages of a 180 symmetric configuration.

The inventors have also developed low-field MRI systems. In some embodiments, the system includes means for providing B for the MRI system ₀ A device for a magnetic field. The device may comprise at least one permanent B ₀ A magnet to generate a magnetic field to contribute to B ₀ A magnetic field. The device may also include a ferromagnetic frame configured to capture and guide at least some of the magnetic fields generated by the B0 magnet. In some embodiments, the frame may include a first post having a first end and a second end, a first multi-pronged member (e.g., a forked member) coupled with the first end, and a second multi-pronged member coupled with the second end. The first and second multiple prong members may support at least one permanent B ₀ A magnet. In some embodiments, an MRI system may include gradient coils configured to generate magnetic fields to provide spatial encoding of Magnetic Resonance (MR) signals, a radio frequency transmit coil, and a power system. The power system may be configured to provide power to the gradient coils and/or the radio frequency transmit coils. In some embodiments, an MRI system may be used to capture at least one MR image.

In some embodiments, a low-field MRI system including a ferromagnetic frame with one or more multi-pronged members according to embodiments described herein may be used to image a patient.

The inventors have recognized that by attaching some or all of the ferromagnetic components to non-ferromagnetic components, a lighter weight, less complex, and better performing furcation frame design may be achieved. Thus, the inventors have developed the following frame design: ferromagnetic blades (e.g., 2 to 8 blades) are attached to the substantially planar non-ferromagnetic assembly, rather than fitting into slots machined in the furcation frame. In this way, assembly and manufacture can be simplified. Additionally, the ferromagnetic blades may be positioned parallel to one of the x-gradient magnetic field or the y-gradient magnetic field rather than radially, which improves gradient field efficiency.

In some embodiments, such a bifurcated frame design may include a connector extending between the first post and the second post and securing the first post to the second post in a direction perpendicular to the ferromagnetic vanes, thereby increasing structural rigidity and providing additional gradient efficiency for the x-gradient magnetic field and/or the y-gradient magnetic field. For example, in some embodiments, the connector includes a ferromagnetic bar (bar) extending between the first post and the second post. The ferromagnetic blades are positioned to extend in a direction substantially perpendicular to the length of the ferromagnetic strip.

In some embodiments, the ferromagnetic strip is formed as a first strip and a second strip. The first and second strips are positioned substantially parallel to each other. In some embodiments, a portion of the first strip is separated from a portion of the second strip by a gap. The gap has a width that is less than one-fourth of the spacing between the first and third multi-pronged members. Alternatively or additionally, the gap has a width in the range from 75mm to 100 mm.

The inventors have recognized that by forming the ferromagnetic frame from a plurality of layered components, the manufacturing complexity of the frame may be reduced. For example, if the frame is constructed as a single piece, the machining of that piece may be more complicated than if the frame were constructed from multiple smaller components (e.g., which may be cut from sheet metal or smaller pieces of material). Additionally, an insulating layer may be interposed between components of the frame to reduce eddy current circulation during operation of the resulting MRI system.

Accordingly, the inventors have developed a method for providing B for a Magnetic Resonance Imaging (MRI) system ₀ Arrangement of magnetic fields, the arrangement comprising at least one permanent B ₀ Magnet and ferromagnetic frame, in which ₀ magnet-to-MRI system B ₀ A magnetic field contributing a magnetic field, the ferromagnetic frame configured to capture and guide the magnetic field by B ₀ At least some of the magnetic fields generated by the magnets. The frame comprisesA first plate and a first post, wherein the first plate is configured to support at least one permanent B ₀ A magnet, the first post attached with the first plate using a first connection fitting. The first connector fitting includes a first connector connecting the first post and the first plate to each other and a second connector attached to the first connector. In some embodiments, the second connector may be configured to provide additional enhancement of magnetic flux within the device.

In some embodiments, the ferromagnetic frame further comprises a second post attached to the first plate using a second connector fitting. The second connector assembly includes a third connector connecting the second post with the first plate and a fourth connector attached to the third connector.

In some embodiments, the ferromagnetic frame further comprises a second plate disposed opposite the first plate and configured to support at least one permanent B ₀ A magnet. The second plate is attached to the first post using a third connector fitting and to the second post using a fourth connector fitting. The third connector assembly includes a fifth connector connecting the first post with the second plate and a sixth connector attached to the fifth connector. The fourth connector assembly includes a seventh connector connecting the second post with the second plate and an eighth connector attached with the seventh connector.

In some embodiments, the first connector comprises a ferromagnetic plate. For example, in some embodiments, the first connector comprises silicon steel. In some embodiments, the first connector is secured to the first post and the first plate using a plurality of fasteners.

In some embodiments, the second connector is secured to the first post by a plurality of fasteners. A plurality of fasteners may pass through the first connector and into the first post to secure the second connector to the first post.

In some embodiments, the ferromagnetic frame further comprises at least one permanent magnet, wherein the permanent magnet is coupled with the inner surface of the first post to provide B ₀ Additional and/or alternative homogenization of the magnetic field. At one endIn some embodiments, the at least one permanent magnet comprises a cylindrical permanent magnet.

In some embodiments, the at least one permanent magnet comprises a first permanent magnet and a second permanent magnet. The first permanent magnet and the second permanent magnet are arranged along a length of the first post. In some embodiments, the first permanent magnet has a first polarization and the second permanent magnet has a second polarization opposite the first polarization. For example, in some embodiments, one of the first polarization and the second polarization is directed toward the inner surface of the first pillar.

The following is a more detailed description of various concepts and embodiments related to ferromagnetic frames for MRI. It should be appreciated that the various aspects described herein may be implemented in any of a number of ways. Examples of specific implementations are provided herein for illustrative purposes only. In addition, the various aspects described in the following embodiments may be used alone or in any combination and are not limited to the combinations explicitly described herein.

FIG. 1 is a block diagram of components of an MRI system 100. In the illustrative example of fig. 1, the MRI system 100 includes a computing device 104, a controller 106, a pulse sequence store 108, a power management system 110, and a magnetic component 120. It should be appreciated that the system 100 is illustrative and that an MRI system may have one or more other components of any suitable type in addition to or instead of the components shown in fig. 1. However, an MRI system will typically include these high-level components, although the implementation of these components for a particular MRI system may differ.

As shown in FIG. 1, the magnetic assembly 120 includes B ₀ A magnet 122, shim coils 124, RF transmit and receive coils 126, and gradient coils 128. The magnet 122 may be used to generate a main magnetic field B ₀ . The magnet 122 may be such as to generate a desired main magnetic field B ₀ Any suitable type of magnetic component or combination of magnetic components. In some embodiments, the magnet 122 may be a permanent magnet, an electromagnet, a superconducting magnet, or a hybrid magnet comprising one or more permanent magnets and one or more electromagnets and/or one or more superconducting magnets. In some embodiments, the magnet 122 may beThe biplane permanent magnets, and in some embodiments, may comprise multiple sets of concentric permanent magnet rings.

The gradient coil 128 may be arranged to provide a gradient field, and may be arranged, for example, to be at B ₀ Gradients are generated in the field in three substantially orthogonal directions (X, Y and Z). The gradient coil 128 may be configured to vary B systematically ₀ The field (B generated by the magnet 122 and/or shim coils 124 ₀ Fields) to encode the emitted MR signals as a function of frequency or phase. For example, the gradient coils 128 may be configured to vary frequency or phase according to a linear function of spatial position along a particular direction, but more complex spatial encoding profiles may also be provided by using non-linear gradient coils.

MRI is performed by exciting and detecting the emitted MR signals using transmit and receive coils, commonly referred to as Radio Frequency (RF) coils, respectively. The transmit/receive coil may comprise a single coil for transmitting and receiving, multiple coils for transmitting and/or receiving, or the same coil for transmitting and receiving. Thus, a transmit/receive component may include one or more coils for transmitting, one or more coils for receiving, and/or one or more coils for transmitting and receiving. The transmit/receive coils are also commonly referred to as Tx/Rx or Tx/Rx coils to generally refer to various configurations of the transmit and receive magnetic components of the MRI system. These terms are used interchangeably herein. In FIG. 1, the RF transmit and receive coil 126 includes a coil that can be used to generate RF pulses to induce an oscillating magnetic field B ₁ One or more than one transmitting coil. The transmit coil(s) may be configured to generate any suitable type of RF pulse.

The power management system 110 includes electronics that provide operating power to one or more components of the low-field MRI system 100. For example, the power management system 110 may include one or more power supplies, gradient power components, transmit coil components, and/or components that provide suitable operating power to power and operate the MRI system 100 componentsAny other suitable power electronics as desired. As shown in fig. 1, power management system 110 includes a power supply 112, power component(s) 114, transmit/receive switch 116, and thermal management component 118 (e.g., cryocooling equipment for superconducting magnets). The power supply 112 includes electronics for providing operating power to the magnetic assembly 120 of the MRI system 100. For example, the power supply 112 may include one or more B' s ₀ Coil (e.g. B) ₀ Magnet 122) provides the electronics that operate to generate the main magnetic field for the low-field MRI system. The transmit/receive switch 116 may be used to select whether the RF transmit coil is being operated or the RF receive coil is being operated.

The power component(s) 114 may include: one or more RF receive (Rx) preamplifiers that amplify MR signals detected by one or more RF receive coils (e.g., coil 126); one or more RF transmit (Tx) power components configured to provide power to one or more RF transmit coils (e.g., coil 126); one or more gradient power components configured to provide power to one or more gradient coils (e.g., gradient coil 128); and one or more shim power assemblies configured to provide power to one or more shim coils (e.g., the shim coils 124).

As shown in fig. 1, the MRI system 100 includes a controller 106 (also referred to as a console) having control electronics to send instructions to the power management system 110 and receive information from the power management system 110. The controller 106 may be configured to implement one or more pulse sequences for determining instructions sent to the power management system 110 to operate the magnetic assembly 120 in a desired sequence (e.g., parameters for operating the RF transmit and receive coils 126, parameters for operating the gradient coils 128, etc.). As shown in fig. 1, the controller 106 also interacts with the computing device 104 programmed to process the received MR data. For example, the computing device 104 may process the received MR data to generate one or more MR images using any suitable image reconstruction process (es). The controller 106 may provide information relating to one or more pulse sequences to the computing device 104 for the computing device to process the data. For example, the controller 106 may provide information related to one or more pulse sequences to the computing device 104, and the computing device may perform image reconstruction processing based at least in part on the provided information.

FIG. 2 depicts a method for providing B for an MRI system in accordance with some embodiments of the technology described herein ₀ Schematic diagram of an apparatus 200 for magnetic fields. The device 200 may comprise B ₀ Magnet 210 and frame 220, wherein frame 220 captures the magnetic field captured by B ₀ The electromagnetic flux generated by magnet 210 and passing the flux to the opposing permanent magnet to increase B ₀ Flux density between the magnets 210. B is ₀ The magnets 210 may be arranged in a bi-planar geometry and may each include a plurality of concentric permanent magnet rings 210a-d, for example, as depicted in fig. 2. In particular, as can be seen in fig. 2, B ₀ The magnet 210 includes a lower portion having a first set of concentric permanent magnet rings comprising: an inner ring of permanent magnets 210a, a first intermediate ring of permanent magnets 210b, a second intermediate ring of permanent magnets 210c, and an outer ring of permanent magnets 210d. B is ₀ The upper portion of the magnet 210 includes another set of concentric permanent magnet rings. In other embodiments, B ₀ The magnet 210 may additionally or alternatively include an electromagnet, a superconducting magnet, other permanent magnets, or any suitable combination thereof.

The permanent magnet material used may be selected according to the design requirements of the system. For example, according to some embodiments, the permanent magnet (or portions of the permanent magnet) may be made of NdFeB that, upon magnetization, produces a magnetic field having a relatively high magnetic field per unit volume of material. According to some embodiments, smCo material is used to form the permanent magnet or parts of the permanent magnet. While NdFeB produces higher field strengths (and is generally less expensive than SmCo), smCo exhibits less thermal drift and therefore provides a more stable magnetic field in the face of temperature fluctuations. Other types of permanent magnetic material(s) may also be used, as aspects of the techniques described herein are not limited in this respect. Usually, one or more than one of the permanent magnetic materials utilizedThe type will depend at least in part on a given B ₀ Field strength, temperature stability, weight, cost, and/or ease of use requirements achieved by the magnet.

The permanent magnet rings 210a-d may be sized and arranged so that the permanent magnet rings 210a-d produce a uniform field of desired intensity in a central region (e.g., field of view and/or imaging region) between the permanent magnets 210. It can be appreciated that B ₀ The magnet 210 may include any suitable number of permanent magnet rings, not just four as depicted in fig. 2. In some embodiments, such as depicted in exemplary fig. 2, the permanent magnet rings 210a-d may be formed from a plurality of permanent magnet blocks. The dimensions (e.g., height, width) of the blocks may be varied to facilitate the generation of a magnetic field of desired strength and uniformity. For example, in some embodiments, the height of the permanent magnet rings may increase away from the center of the magnet. For example, in some embodiments, the height of the permanent magnet ring 210b may be greater than the height of the permanent magnet 210a, the height of the permanent magnet ring 210c may be greater than the height of the permanent magnet 210b, and the height of the permanent magnet 210d may be greater than the height of the permanent magnet 210d. Title "B" submitted in 2019, 5 months and 20 days ₀ Aspects of varying heights and/or widths of concentric permanent Magnet rings are further described in U.S. patent publication No. 2019/0353726 to Magnetic Methods and Apparatus For a Magnetic Resonance Imaging System, "which is incorporated herein by reference in its entirety.

The device 200 further comprises a frame 220, the frame 220 being configured to capture the message by B ₀ Magnetic flux generated by the magnet 210 and directed to B ₀ Opposite sides of the magnet to increase B ₀ Magnetic flux density between the magnets 210, thereby increasing B ₀ The field strength within the field of view of the magnet. By capturing and directing magnetic flux to B ₀ The region between the magnets 210, may be at B ₀ Less permanent magnet material is used in the magnet 210 to achieve the desired field strength, thereby reducing B ₀ Size, weight and cost of the magnets. Alternatively, for a given permanent magnet, the field strength can be increased, thereby improving the signal-to-noise ratio (SNR) of the system without having to use an increased amount of permanent magnet material.

For the exemplary device 200, the frame 220 includes a first column 222a and a second column 222b, the first column 222a having a first end 223a and a second end 223b, the second column 222b having a third end 223c and a fourth end 223d.

Multiple prong members

224a, 224b are coupled with the first end 223a and the second end 223b of the first column 222a, and

multiple prong members

224c, 224d are coupled with the third end 223c and the fourth end 223d of the second column 222 b. The multiple-prong members 224a-d may be coupled with the first and

second posts

222a, 222b by a stem member 226.

As shown in fig. 2, the first and second posts 222a and 222B may be positioned opposite each other at an angle of 180 ° such that B is ₀ The magnet 210 is positioned between the first post 222a and the second post 222 b. However, it can be appreciated that the first and second posts 222a, 222B can be positioned at an angle other than 180 ° (e.g., 120 °) to increase the pair B ₀ Accessibility to one side of the field of view of the magnet 210 while maintaining most of the advantages of symmetry of the device 200. For example, in some embodiments, the first and

second posts

222a, 222b may be positioned at any angle ranging from 100 ° to 180 ° (e.g., 120 °, 135 °, 150 °, 165 °, or 180 °). Alternatively, in other embodiments, the first and

second posts

222a, 222b may be positioned at any angle in the range from 120 ° to 145 °.

Multiple prong members 224a-d may be captured by B ₀ The magnets 210 generate electromagnetic flux and direct the electromagnetic flux to the first and

second posts

222a, 222b to circulate via the magnetic return path of the frame. According to some embodiments of the techniques described herein, the electromagnetic flux capture may increase B ₀ Flux density in the field of view of the magnet. As shown in fig. 2, the multi-pronged members 224a-d include two prongs with a collector region 229 disposed between the two prongs. However, in other embodiments, the multi-prong members 224a-d may include two or more prongs (e.g., 4 prongs, 6 prongs) to occupy the collector area 229 and increase the number of B-prongs ₀ The capture of the electromagnetic flux generated by the magnet 210.

In some embodiments, the frame 220 including the multi-prong members 224a-d and the first and

second posts

222a, 222b may be constructed of any desired ferromagnetic material (e.g., low carbon steel and/or CoFe, and/or silicon steel, etc.) to provide the frame 220 provides the desired magnetic properties. In some embodiments, the first and

second posts

222a, 222b and/or the multi-prong members 224a-d may be constructed of laminated ferromagnetic materials (e.g., any of the ferromagnetic materials described above) to reduce the continuous circulation of eddy currents around the cross-section of the multi-prong members 224 a-d. In such embodiments, the first and second posts 222a, 222B and/or the multiple-prong members 224a-d may be arranged in a pattern B ₀ The plane of the magnet 210 is formed as a laminate in a substantially orthogonal plane.

In some embodiments, the multi-pronged members 224a-d may be configured to support B as described herein, including with reference to fig. 6A-6C ₀ A non-conductive component (not depicted in fig. 2) of the magnet 210 is attached. The multiple prong members 224a-d may generally be designed to reduce the amount of magnetic material required to support the permanent magnets while still being supported by B ₀ The return path of the magnetic flux generated by the magnet 210 provides a sufficient cross section. Such a design may be up to 20% lighter than a C-shaped frame (e.g., for a B with an accessible gap of 35cm and providing 65mT on a 20cm diameter sphere ₀ Magnetic field and 500ppm peak-to-peak (peak-to-peak) shimming homogeneity, weighing between about 220kg and 300 kg).

Additionally, because the multi-prong members 224a-d reduce the amount of magnetic material used in the frame 220, the multi-prong members 224a-d also reduce the surface area available for eddy current conduction during operation of the gradient coils of the MRI system. This reduction may result in a reduction of the time constant of the MRI system and an increase of the overall gradient field efficiency.

Further, in some embodiments, as shown in exemplary FIG. 2, the multiple-prong members 224a-d may be arranged with a gap 228 between the ends of the opposing multiple-prong members 224 a-d. Gap 228 may be an air gap. Such an air gap may eliminate a conductive path across the direction between opposing posts 222. Accordingly, the gap 228 may also reduce eddy current conduction in the frame 220 during MR imaging.

As depicted in the example of fig. 2, a collector region 229 (e.g., B) ₀ An open area above the magnet 210) may be located between the multiple-prong members 224 a-d. The collector region 229 may direct electromagnetic flux from the magnet ring to the first and second legs 222a and 222bIn the two columns 222 b. The collector region 229 may also provide enhancement to the gradient field by including a plurality of conductive vanes 340 as depicted in the example of fig. 3.

Fig. 3 illustrates an embodiment of a device 300 having blades 340, wherein the blades 340 are configured to enhance a gradient magnetic field generated by an MRI system including the device 330, in accordance with some embodiments of the techniques described herein. The vanes 340 may be arranged in a sparse manner to cover the surface behind the gradient coils (not depicted) to provide improved gradient field efficiency while minimizing eddy current conduction. The apparatus 300 may include a plurality of vanes 340 (such as 16 or 24 vanes, etc.) to provide improved gradient field efficiency. Alternatively, the apparatus 300 may include a plurality of blades 340 ranging from 16 to 24 blades or ranging from 8 to 32 blades.

In some embodiments, the vanes 340 may be arranged in a radial fashion, extending between the multi-pronged members 224a-d toward a common center in the collector region 229. The blades 340 may not meet or touch the common center in order to prevent a conduction path of eddy currents from forming between opposing blades 340. As a result, the eddy current time constant of the exemplary apparatus 300 may be less than half the eddy current time constant of a comparable C-shaped design. Although not shown in fig. 3, in some embodiments, the vanes 340 can be coupled with one or more non-conductive elements at a common center of the collector region 229 for stability (e.g., the ends closer to the center can be slid into plastic slots as shown by the non-conductive elements 660 of fig. 6A).

According to some embodiments of the techniques described herein, although the blades 340 may increase the weight of the apparatus 300, the blades 340 also increase the weight of the slave B ₀ The magnet 210 collects the electromagnetic flux, thereby increasing the DC field efficiency. The increased DC field efficiency provided by the vanes 340 may allow for a reduction in B ₀ The weight of the permanent magnet material used in the magnet 210, potentially reducing the overall raw material cost of the apparatus 300.

In some embodiments, to provide improved gradient field efficiency, the vanes 340 may be formed from a ferromagnetic material. The vanes may be formed of, for example, low carbon steel, coFe, and/or silicon steel to provide the desired magnetic properties. The blade 340 may be formed of the same ferromagnetic material as the frame 220, or may be formed of a different ferromagnetic material than the frame 220.

In some embodiments, the vanes 340 may be formed separately from the multi-pronged members 224 a-d. The blades may be coupled with the multi-pronged members 224a-d by, for example, being inserted into machined slots (not depicted) in the multi-pronged members 224 a-d. In such embodiments, the blades 340 may be formed by, for example, stamping or laser cutting from sheet metal. Alternatively, the vanes 340 and the multi-prong members 224a-d may be cast together as a single piece to reduce the number of parts required for assembly.

In some embodiments, the blades 340 may be specifically sized to provide desired magnetic properties. For example, the vanes 340 may be high enough to avoid B ₀ The magnet 210 is magnetically saturated to provide enhancement to the gradient coils. However, the vanes 340 may not be too high, otherwise the vanes 340 will provide additional surface area for vortex conduction. For example, the vanes 340 may be about half the height of the multi-pronged members 224a-d to provide these desired magnetic characteristics. Similarly, the vanes 340 may be thin to reduce eddy current conduction caused by the additional material. For example, in some embodiments, the width of the vane 340 may be about 5mm. Alternatively, the vanes 340 may be made thicker, while the total number of vanes 340 may be reduced to reduce assembly complexity.

In some embodiments, the vanes 340 may have a constant profile along the length of the vanes 340. In other embodiments, the vanes 340 may have a tapered profile along the length of the vanes 340. Examples of such blade profiles are depicted in fig. 4A-4C. Fig. 4A illustrates an example of a vane 340 having a constant height H and a constant width W along a length of the vane 340 in accordance with some embodiments of the technology described herein.

Fig. 4B illustrates an example of a blade 340 having a tapered width in accordance with some embodiments of the technology described herein. The width of the vane 340 changes along the length of the vane from a first width W1 at a first end of the vane 340 to a smaller second width W2 at a second end of the vane 340. The first end of the blade may be the end to which the multi-pronged members 224a-d of the apparatus 300 are attached such that the second end is positioned near the common center of the collector area.

Fig. 4C illustrates an alternative example of a vane 340 having a tapered height in accordance with some embodiments of the technology described herein. The height of the vane 340 may vary along the length of the vane from a first height H1 at a first end of the vane 340 to a smaller second height H2 at a second end of the vane 340. The first ends of the blades may be attached with the multi-pronged members 224a-d of the apparatus 300 such that the second ends are positioned near the common center of the collector area.

Fig. 5 depicts a flowchart directed to providing B for an MRI system, in accordance with some embodiments of the technology described herein ₀ Different configurations of the device of magnetic fields simulate gradient field decay over time. At time equal to zero, the simulated gradient field along the single axis falls off rapidly. The gradient field then decays at different rates depending on the structure in the vicinity of the gradient coil. The three curves from top to bottom show the gradient field decay over time for the following devices: comprising a support B ₀ Apparatus for solid plates of magnets, including arrangement at B ₀ Apparatus for vanes (e.g., vanes 340) near magnets, and apparatus included in B ₀ An empty space near the magnet (e.g., a collector region 229 between the tines of the multi-tine member 224a-d as shown in fig. 2). The vane configuration provides faster gradient field attenuation than the more conventional solid plate configuration. The empty space configuration produces 12mT/m at full current, while the blade configuration produces 14.7mT/m at full current. The solid plate provides 15.6mT/m.

Fig. 6A-6C depict a method for providing B for an MRI system, in accordance with some embodiments of the technology described herein ₀ Different diagrams of an apparatus 600 for magnetic fields. The apparatus 600 is similar to the apparatus 300 of fig. 3, but includes

non-conductive support structures

650a and 650b above and below the multiple-prong members 224 a-d. The device 600 further includes a non-conductive element 660 coupled to the center end of the blade 340. The

non-conductive support structures

650a and 650b and/or the non-conductive elements 660 can be made of any suitable non-conductive material, including but not limited to plastic and/or fiberglass.

In some embodiments, the

non-conductive support structures

650a and 650b may be slotted to provide positioning and support for the blade 340. Additionally, the

non-conductive support structures

650a and 650b may protect the blade 340 from environmental damage (e.g., dust, dirt). The non-conductive support structure 650B may support B ₀ Magnet 210, wherein B ₀ The magnet 210 may be mounted directly to a surface of the non-conductive support structure 650b. In some embodiments, such surfaces may be substantially planar.

The inventors have developed a portable, low power MRI system that can be brought to the patient where MRI is needed, using the techniques described herein, thereby providing an affordable and widely deployable MRI. Fig. 7 illustrates an example of a portable low-field MRI system 700 including the apparatus 300 of fig. 3, in accordance with some embodiments of the technology described herein. The apparatus 300 may be supported by a base 710. The base 710 may house the power components and/or electronics discussed in connection with fig. 1 (including the power components configured to operate the MRI system 700).

In accordance with some embodiments of the techniques described herein, the base 710 may also include one or more transport mechanisms 720 that enable the MRI system 700 to be used at the point-of-care. In the example of fig. 7, transport mechanism 720 is depicted as wheels, but other transport mechanisms may be used. In some embodiments, the transport mechanism 720 may include a motorized assembly 725, the motorized assembly 725 may be configured to allow the MRI system 700 to be driven from one location to another, for example, using controls such as joysticks or other control mechanisms disposed on the MRI system 700 or remote from the MRI system 700. In this manner, as shown in fig. 8, the MRI system 700 may be transported to the patient and maneuvered to the bedside for imaging.

Fig. 8 depicts a brain scan of a patient using the portable MRI system of fig. 7 in accordance with some embodiments of the techniques described herein. During a brain scan, the MRI system 700 may be used to capture at least one magnetic resonance image of a patient for clinical use.

As described herein, in some embodiments, the blades may be arranged in a radial manner. However, in some embodiments, it may be desirable to employAn alternative arrangement is used. One example of such an alternative arrangement is shown in fig. 9A-9D, where fig. 9A-9D depict a method for providing B for an MRI system in accordance with some embodiments of the techniques described herein ₀ Different views of the device 900 of magnetic fields, the assembly includes ferromagnetic connectors and blades. Fig. 9A shows the device 900 in a partially disassembled state, and fig. 9B shows a top view of the device 900 in a partially disassembled state. Fig. 9C and 9D show the device 900 assembled with the laminate 940 and the gasket 950, respectively, in exploded views.

For example, in some embodiments and as shown in fig. 9A and 9B, device 900 includes B ₀ Magnet 910 and frame, wherein the frame captures the magnetic field from B ₀ The electromagnetic flux generated by magnet 910 and passing the flux to the opposing permanent magnet to increase B ₀ Flux density between magnets 910. As described in connection with the embodiment of fig. 2, B ₀ The magnets 910 are arranged in a bi-planar geometry and may each include, for example, a plurality of concentric permanent magnet rings.

In some embodiments, the frame includes a post 922 coupled with a multi-pronged member 924, as described in connection with the example of fig. 2. The frame also includes one or more connectors 925 that extend between opposite ends of the posts 922. The connector 925 may secure the plurality of posts 922 to one another. In some embodiments, the connector 925 may be positioned between the multi-pronged members 924.

In some embodiments, the connector 925 may be an elongate strip extending between the posts 922. As shown in fig. 9B, the strip may have a middle portion with a reduced thickness relative to the ends of the strip. In some embodiments, the frame may include a plurality of connectors 925 (e.g., two, or more than two, etc.), and the connectors 925 may be positioned substantially parallel to each other. The connection 925 can also be positioned substantially parallel to the direction of one of the gradient fields (e.g., one of the X-gradient field or the Y-gradient field) to enhance the generated gradient field strength during MR imaging.

In some embodiments, a gap G1 may exist between the middle portions of connecting members 925. The width of the gap G1 may be about 80mm, or the width may be in the range from 75mm to 100 mm. Alternatively, in some embodiments, the width of the gap G1 may be determined relative to the length of the post 922 (e.g., the distance between the opposing multi-pronged members 924 of the frame). For example, the width of the gap G1 may be less than one-quarter of the length of the post 922. Limiting the width of gap G1 and the thickness of connector 925 can reduce the magnitude of eddy currents circulating through the frame during MR imaging.

In some embodiments, the frame, including the post 922, the multi-prong member 924, and the connector 925 may be constructed of any desired ferromagnetic material (e.g., low carbon steel and/or CoFe and/or silicon steel, etc.) to provide the frame with desired magnetic properties. In some embodiments, the post 922, the multi-prong member 924, and/or the connector 925 can be constructed from laminated ferromagnetic materials (e.g., any of the ferromagnetic materials described above) in order to reduce the continuous circulation of eddy currents around the cross-section of the multi-prong member 924 and/or the connector 925. In such embodiments, the first and second posts 922, the multi-prong member 924, and/or the connector 925 may be disposed at the same location as B ₀ The ring of magnets 910 is formed of a laminate in a plane that is substantially orthogonal to the plane in which the ring lies.

In some embodiments, the apparatus 900 may include a blade 926. The blade 926 may be similar to the blade 340 of the apparatus 300 as described in connection with fig. 3. However, the vanes 926 may be aligned substantially parallel to the direction of one of the gradient fields (e.g., one of the X-gradient field or the Y-gradient field), rather than in a radial direction as in the apparatus 300. The vanes 926 may be aligned substantially parallel to the direction of one of the gradient fields to provide improved gradient field efficiency during operation of the MRI system. The apparatus 900 may include a plurality of vanes 926, such as 4 or 6 vanes, etc., to provide improved gradient field efficiency. Alternatively, the apparatus 900 may include a plurality of blades 926 ranging from 2 to 8 blades. In the example of fig. 9A and 9B, four blades 926 (which are positioned in pairs on either side of the connection 925) are shown. Each pair of vanes 926 may be separated by a gap G2 having a width of approximately 127.4 mm. In some embodiments, the width of the gap G2 may be in the range from 110mm to 140 mm.

In some embodiments, to provide improved gradient field efficiency, the vanes 926 may be formed from a ferromagnetic material. The vanes may be formed of, for example, low carbon steel, coFe, and/or silicon steel to provide the desired magnetic properties. The blade 926 may be formed from the same ferromagnetic material as the other components of the frame, or may be formed from a different ferromagnetic material than the frame.

In some embodiments, the blade 926 may be formed separately from the multi-pronged member 924 and/or the connector 925. In such an embodiment, the blade 926 may be formed by, for example, stamping or laser cutting from sheet metal. Alternatively, the blade 926, the multi-pronged member 924, and the connector 925 may be cast together as a single piece to reduce the number of parts required for assembly.

In some embodiments, the blade 926 may have a constant profile along the length of the blade 926, similar to the example of the blade 340 depicted in fig. 4A. Fig. 4A shows an example of a blade having a constant height H and a constant width W along the length of the blade. In some embodiments, the vanes 926 may have a constant width of about 7.5mm or a constant width in the range from 5mm to 10 mm. In some embodiments, the vanes 926 may have a constant height of about 66mm or a constant height in the range from 50mm to 100 mm. In some embodiments, the blade 926 may have a constant length of about 190mm or in the range from 170mm to 210 mm.

In some embodiments, blades 926, multi-pronged members 924, and/or connectors 925 may be configured to support apparatus 900 and B ₀ The non-conductive component of the magnet 910 is attached. For example, each multi-pronged member 924 may be secured to and spaced apart from an opposing multi-pronged member 924 by a spacer 928. In some embodiments, spacer 928 may be formed from plastic or any other suitable non-conductive material. Additionally, the spacer 928 may be configured to provide a rigid non-conductive support 930.

In some embodiments, the device may include one or more non-conductive supports 930, where the non-conductive supports 930 are configured to cover a component of the frame and are B ₀ The magnet 910 and blade 926 provide support. In some embodiments, the structural foam may be intercalated with non-electrical conductivityIn the space between the support 930, the multi-pronged member 924, the connector 925, and/or the blade 926. The non-conductive support 930 may be formed of a non-conductive laminate material such as G-10. The non-conductive support 930 may be positioned on an outward facing surface of the multi-prong member 924 and/or an inward facing surface of the multi-prong member 924 with B ₀ Between magnets 910, wherein "facing inward" indicates facing B ₀ The region between magnets 910. Because the blade 926 is secured to the non-conductive support 930 rather than the multi-pronged member 924, the slots in the multi-pronged member 924 may not be machined, thereby reducing the manufacturing complexity of the apparatus 900 relative to the apparatus 300 and/or 600.

In some embodiments, the non-conductive support 930 may be fastened to the multi-pronged member 924 and the connector 925 by fasteners 932 in some embodiments. The fastener may extend through the multi-pronged member 924 and/or the connector 925 into the post 922. Additionally, in some embodiments, the blade 926 may be fastened to the non-conductive support 930 by additional fasteners (not shown) extending through the non-conductive support 930 into the blade 926.

In some embodiments, as shown in the examples of fig. 9C and 9D, device 900 may include a laminate 940 and/or a gasket 950. The laminate 940 may be positioned at B ₀ The magnet 910 is on the inward facing surface and thereafter a shim 950 may be placed on the laminate 940. In some embodiments, the laminate 940 may include at least one conductive layer patterned to form one or more gradient coils or a portion of one or more gradient coils, the at least one conductive layer being capable of generating or contributing a magnetic field suitable for providing spatial encoding of detected MR signals when operating in a low-field MRI device. In some embodiments, the laminate may include one or more conductive layers patterned to form one or more X-gradient coils (or portions of X-gradient coils), one or more Y-gradient coils (or portions of Y-gradient coils), and/or one or more Z-gradient coils (or portions of Z-gradient coils).

Alternatively or additionally, the laminate 940 may include at least one conductive layer (which is patterned to form one or more conductive layers)At one transmitting and/or receiving coil or a portion of one or more transmitting and/or receiving coils), wherein at least one conductive layer is configured to be in contact with (configured to produce B) ₀ Fields and/or corresponding gradient fields for spatially encoding the received MR signals) by generating B ₁ The excitation field (transmit) stimulates the MR response and/or receives the emitted MR signals (receive). Further, in some embodiments, the laminate 940 may include additional magnetic components, such as one or more shim coils or the like, wherein the shim coils are arranged to generate a magnetic field to support the system to, for example, increase B ₀ The strength and/or uniformity of the field, counteract deleterious field effects (such as those created by the operation of gradient coils, loading effects of the object being imaged, etc.), or otherwise support the magnetic properties of the low-field MRI system. Additional details regarding the fabrication and construction of such laminates are provided in U.S. patent 10,495,712 entitled "Low Field Magnetic Resonance Imaging Methods and assemblies," filed 2017, 9/29, which is incorporated herein by reference in its entirety.

In some embodiments, shims 950 may be positioned adjacent to laminate 940 and configured to improve uniformity and provide B within the imaging zone of the MRI system ₀ Correction of the field strength of the magnetic field. For example, a passive piece of ferromagnetic material (e.g., steel) may be positioned to adjust the B of the MRI system ₀ A magnetic field distribution. For example, shim 950 may be formed to have been magnetized in a desired pattern to produce a magnetic field to improve B ₀ A magnetic material sheet having a distribution of magnetic field. The shim 950 is shown in the example of fig. 9B as including two pieces of magnetic material (the lower piece) and a plastic retainer (the top) configured to position the orientation of the shim and secure the shim to the laminate 940. It should be appreciated that in some embodiments, the shim 950 may include fewer or more than two pieces of magnetic material. Additional details regarding the fabrication and construction of Magnetic sheet spacers are provided in U.S. patent 10,613,168, entitled "Methods and Apparatus for Magnetic Field shifting," filed on 2017, 3, month 22, which is incorporated herein by reference in its entirety.

10A-10B illustrate a method for providing B for an MRI system in accordance with some embodiments of the technology described herein ₀ A diagram of an apparatus 1000 for magnetic fields. In some embodiments, device 1000 includes posts 1022 that are secured to plates 1030 by connector fittings 1024. Plate 1030 may be configured to support B ₀ A magnet 1010.

In some embodiments, the connector fitting 1024 may include a first connector 1024a and a second connector 1024b. First connector 1024a can connect one of posts 1022 with one of plates 1030. For example, and as shown in fig. 10B, first connector 1024a may be a substantially planar plate extending above plate 1030 such that fastener 1025a may extend through first connector 1024a and secure first connector 1024a to plate 1030. The first connector 1024a can be secured to the post 1022 with an additional fastener 1025b (extending through the second connector 1024b, the first connector 1024a, and the post 1022). Forming connector assembly 1024 from multiple "layered" components may reduce manufacturing costs (e.g., by simplifying manufacturing processes). In some embodiments, an insulating component (not shown) may be interposed between components of the connector fitting 1024 and/or between the connector fitting 1024 and the posts 1022 to reduce or mitigate eddy current circulation in the apparatus 1000.

In some embodiments, the second connector 1024b can be configured to increase the magnetic flux capability of the device 1000. For example, the second connector 1024B may have a wedge shape as shown in the example of fig. 10A and 10B to direct and concentrate magnetic flux from the pole 1022 back to B ₀ In the imaging zone between magnets 1010.

In some embodiments, plate 1030 may be configured to support B ₀ A magnet 1010. Plate 1030 may be formed of a solid ferromagnetic sheet material. In some embodiments, plate 1030 may include one or more holes to reduce the weight of plate 1030 and/or to allow cooling or ventilation of device 1000 during MR imaging.

In some embodiments, the posts 1022, the connecting fittings 1024, and the plates 1030 may be constructed of any desired ferromagnetic material (e.g., low carbon steel and/or CoFe and/or silicon steel, etc.) to provide a stand for the apparatus 1000Providing desired magnetic properties. In some embodiments, posts 1022, connector assemblies 1024, and/or plate 1030 may be constructed of laminated ferromagnetic materials (e.g., any of the ferromagnetic materials described above) to reduce the continuous circulation of eddy currents around the cross-section of connector assemblies 1024 or plate 1030. In such embodiments, post 1022, connector fitting 1024, and/or plate 1030 may be connected to B ₀ The plane of the magnet 1010 is formed of a laminate arranged in a substantially orthogonal plane.

In some embodiments, the apparatus 1000 may include additional permanent magnets 1026 on the inward facing surfaces of the columns 1022. The permanent magnet 1026 may be positioned and/or shaped to reduce B ₀ Inhomogeneity of the magnetic field, and may be referred to as B ₀ Shim coils and/or passive shims positioned adjacent the magnet 1010 may be used in addition to or instead of. For example, the cross-sectional shape of the permanent magnet 1026 may be cylindrical or elliptical. The permanent magnets 1026 may be disposed along the length of the columns 1022.

In some embodiments, the permanent magnets 1026 may be polarized in a direction perpendicular to the plane of the inward-facing surfaces of the posts 1022 (e.g., toward or away from the concentric B) ₀ Common center of permanent magnet ring 1010). In some embodiments with two permanent magnets 1026, each of the two permanent magnets 1026 may have opposite polarizations. For example, a first of the permanent magnets 1026 may have a polarization that is directed toward the inward-facing surface of the pole 1022, and a second of the permanent magnets 1026 may have a polarization direction that is directed away from the inward-facing surface of the pole 1022.

It should be appreciated that while the example of fig. 10A and 10B shows two permanent magnets 1026 attached to each post 1022, in some embodiments additional permanent magnets 1026 or fewer permanent magnets 1026 may be used. It should also be appreciated that permanent magnet 1026 may be included in any of the embodiments described herein, including

devices

200, 300, 600, 900, and/or 1000.

Having thus described several aspects of at least one embodiment of this technology, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art.

Various aspects of the technology described herein may be used alone, in combination, or in a variety of arrangements not specifically described in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

Use of ordinal terms such as "first," "second," "third," etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having," "containing," "involving," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

The terms "about," "substantially," and "about" may be used in some embodiments to mean within 20% of a target value, in some embodiments to mean within 10% of a target value, in some embodiments to mean within 5% of a target value, and in some embodiments to mean within 2% of a target value. The terms "about," "substantially," and "about" may include the target value.

Claims

1. For providing B to MRI system ₀ An apparatus for magnetic fields, the apparatus comprising:

at least one permanent B ₀ Magnet to B of the MRI system ₀ The magnetic field contributes to the magnetic field; and

a ferromagnetic frame configured to capture and guide at least one permanent B ₀ At least some of the magnetic fields generated by the magnets, the frame comprising:

a first post having a first end and a second end;

a first multi-pronged member coupled with the first end; and

a second multi-pronged member coupled with the second end,

wherein the first and second multi-pronged members support the at least one permanent B ₀ A magnet.

2. The apparatus of claim 1, wherein the ferromagnetic frame further comprises:

a second post having a third end and a fourth end;

a third multi-pronged member coupled with the third end; and

a fourth multi-pronged member coupled with the fourth end.

3. The device of claim 2 or any other preceding claim, wherein the first and second posts are secured to each other by at least one ferromagnetic connector.

4. The apparatus of claim 3 or any other preceding claim, wherein the at least one ferromagnetic connector comprises at least one ferromagnetic strip.

5. The apparatus of claim 4 or any other preceding claim, wherein the at least one ferromagnetic strip further comprises at least one blade having a length extending in a direction substantially perpendicular to the length of the at least one ferromagnetic strip.

6. The apparatus of claim 5 or any other preceding claim, wherein the at least one ferromagnetic strip further comprises a first strip and a second strip.

7. The apparatus of claim 6 or any other preceding claim, wherein the first strip is arranged substantially parallel to the second strip.

8. The apparatus of claim 7 or any other preceding claim, wherein a portion of the first strip is separated from a portion of the second strip by a gap.

9. The apparatus of claim 8 or any other preceding claim, wherein the gap has a width that is less than one-quarter of a spacing between the first and second multi-pronged members.

10. The apparatus of claim 8 or any other preceding claim, wherein the gap has a width in a range from 75mm to 100 mm.

11. The apparatus of claim 2 or any other preceding claim, further comprising at least one spacer that secures the first multi-pronged member to the third multi-pronged member and the second multi-pronged member to the fourth multi-pronged member.

12. The apparatus of claim 11 or any other preceding claim, wherein the at least one spacer comprises plastic.

13. The device of claim 1 or any other preceding claim, wherein the first post, the first multi-pronged member, and the second multi-pronged member each comprise a ferromagnetic material.

14. The device of claim 2 or any preceding claim, wherein the second, third, and fourth multi-prong members each comprise a ferromagnetic material.

15. The apparatus of claim 1 or any other preceding claim, wherein the first multi-pronged member includes a stem and two prongs coupled with the stem, wherein the two prongs are spaced apart from each other by a gap.

16. The apparatus of claim 15 or any other preceding claim, wherein each of the two prongs is curved.

17. The apparatus of claim 2 or any other preceding claim, wherein the first multi-pronged member is disposed opposite the third multi-pronged member with a gap therebetween.

18. The apparatus of claim 17 or any other preceding claim, wherein the gap is an air gap.

19. The apparatus of claim 17 or any other preceding claim, wherein the second multi-pronged member is disposed opposite the fourth multi-pronged member with a gap therebetween.

20. The apparatus of claim 2 or any other preceding claim, wherein the at least one permanent B ₀ The magnet is a biplane magnet comprising a first concentric permanent magnet ring and a second concentric permanent magnet ring.

21. The apparatus of claim 20 or any other preceding claim,

wherein the first and third multi-pronged members support the first concentric permanent magnet ring, an

The second and fourth multiple prong members support the second concentric permanent magnet ring.

22. The apparatus of claim 20 or any other preceding claim,

wherein the first and third multiple prong members are coupled with a first non-conductive component and the first concentric permanent magnet ring is disposed on a surface of the first non-conductive component, an

The second and fourth multiple prong members are coupled with a second non-conductive component, and the second concentric permanent magnet ring is disposed on a surface of the second non-conductive component.

23. The apparatus of claim 22 or any other preceding claim, wherein the first and second non-conductive components are substantially planar.

24. The apparatus of claim 2 or any other preceding claim, further comprising a first plurality of ferromagnetic vanes.

25. The apparatus of claim 24 or any other preceding claim, wherein an end of each ferromagnetic vane of the first plurality of ferromagnetic vanes is coupled with the first or third multi-pronged member.

26. The apparatus of claim 24 or any other preceding claim, wherein an end of each ferromagnetic vane of the first plurality of ferromagnetic vanes is disposed within a slot formed within the first or third multi-pronged member.

27. The apparatus of claim 24 or any other preceding claim, wherein ferromagnetic vanes of the first plurality of ferromagnetic vanes are arranged to extend radially from a common center.

28. The apparatus of claim 27 or any other preceding claim, wherein a blade of the first plurality of ferromagnetic blades does not contact the common center.

29. The apparatus of claim 24 or any other preceding claim, wherein a height of each ferromagnetic blade of the first plurality of ferromagnetic blades varies along a length of the each ferromagnetic blade.

30. The apparatus of claim 24 or any other preceding claim, wherein a width of each ferromagnetic blade of the first plurality of ferromagnetic blades varies along a length of the each ferromagnetic blade.

31. The apparatus of claim 24 or any other preceding claim, wherein the first plurality of ferromagnetic vanes comprises at least 16 vanes and at most 24 vanes.

32. The apparatus of claim 24 or any other preceding claim, wherein the first plurality of ferromagnetic vanes consists of between 10 and 30 vanes.

33. The apparatus of claim 24 or any other preceding claim, wherein each ferromagnetic vane of the first plurality of ferromagnetic vanes comprises silicon steel.

34. The apparatus of claim 24 or any other preceding claim, further comprising a second plurality of ferromagnetic vanes.

35. The apparatus of claim 34 or any other preceding claim, wherein an end of each ferromagnetic vane of the second plurality of ferromagnetic vanes is coupled with the second or fourth multi-pronged member.

36. The apparatus of claim 24 or any other preceding claim, wherein each ferromagnetic vane of the first plurality of ferromagnetic vanes is aligned to extend along a direction substantially parallel to one of an x-gradient magnetic field and a y-gradient magnetic field.

37. The apparatus of claim 36 or any other preceding claim, wherein the first plurality of ferromagnetic vanes consists of between 2 and 8 vanes.

38. The apparatus of claim 24 or any other preceding claim, wherein the first and second posts are secured to one another by at least one strip, and wherein each ferromagnetic leaf of the first plurality of ferromagnetic leaves is aligned to extend in a direction substantially perpendicular to a length of the at least one strip.

39. The apparatus of claim 2 or any other preceding claim, wherein the first and second posts are arranged at an angle of 180 ° such that the at least one permanent B is ₀ A magnet is disposed between the first post and the second post.

40. The apparatus of claim 2 or any other preceding claim, wherein the first and second posts are arranged at an angle in a range from 100 ° to 180 °.

41. The apparatus of claim 2 or any other preceding claim, wherein the first and second posts are arranged at an angle in a range from 120 ° to 145 °.

42. The apparatus of claim 2 or any other preceding claim, further comprising at least one permanent magnet coupled with an inner surface of the first post.

43. The apparatus of claim 42 or any other preceding claim, wherein the at least one permanent magnet comprises at least one cylindrical permanent magnet.

44. The apparatus of claim 43 or any preceding claim, wherein the at least one permanent magnet comprises a first permanent magnet and a second permanent magnet, the first permanent magnet being disposed adjacent a first end of the first post, and the second permanent magnet being disposed adjacent a second end of the first post.

45. The apparatus of claim 44 or any preceding claim, wherein the first permanent magnet has a first polarization and the second permanent magnet has a second polarization opposite the first polarization.

46. The apparatus of claim 45 or any preceding claim, wherein one of the first polarization and the second polarization is directed towards an inner surface of the first pillar.

47. The apparatus of claim 43 or any preceding claim, further comprising at least one permanent magnet coupled to an inner surface of the second post.

48. The apparatus of claim 47 or any preceding claim, wherein the at least one permanent magnet coupled to the inner surface of the second column comprises a third permanent magnet and a fourth permanent magnet, the third permanent magnet disposed adjacent a third end of the second column and the fourth permanent magnet disposed adjacent a fourth end of the second column.

49. The apparatus of claim 48 or any preceding claim, wherein the third permanent magnet has a third polarization and the second permanent magnet has a fourth polarization opposite the third polarization.

50. The device of claim 49 or any preceding claim, wherein one of the third polarization and the fourth polarization is directed towards an inner surface of the second column.

51. A magnetic resonance imaging system comprising:

the apparatus of claim 1;

a plurality of gradient coils configured to generate magnetic fields when operated to provide spatial encoding of the emitted magnetic resonance signals;

at least one radio frequency transmit coil; and

a power system configured to provide power to the plurality of gradient coils and the at least one radio frequency transmit coil.

52. A method, comprising:

imaging a patient using a Magnetic Resonance Imaging (MRI) system, the MRI system comprising:

at least one permanent B ₀ Magnet to B of the MRI system ₀ A magnetic field contribution field; and

a ferromagnetic frame configured to capture and guide the at least one permanent B ₀ At least some of the magnetic fields generated by the magnets, the ferromagnetic frame comprising:

a first post having a first end and a second end;

a first multi-pronged member coupled with the first end; and

a second multi-pronged member coupled with the second end,

53. For capturing and guiding B ₀ A framework of at least some of the magnetic fields, said B ₀ The magnetic field is generated by a Magnetic Resonance Imaging (MRI) system, the frame comprising:

a ferromagnetic frame configured to capture and guide at least one permanent B ₀ The B generated by magnet ₀ At least some of the magnetic fields, the ferromagnetic frame comprising:

a first post having a first end and a second end;

a first multi-pronged member coupled with the first end; and

a second multi-pronged member coupled with the second end,

54. The frame according to claim 53, wherein said ferromagnetic frame further comprises:

a second post having a third end and a fourth end;

a third multi-pronged member coupled with the third end; and

a fourth multi-pronged member coupled with the fourth end.

55. The frame of claim 54 or any other preceding claim, wherein the first and second posts are secured to each other by at least one ferromagnetic connector.

56. The frame of claim 54 or any other preceding claim, wherein the at least one ferromagnetic connector comprises at least one ferromagnetic strip.

57. The frame according to claim 56 or any other preceding claim, wherein said at least one ferromagnetic strip further comprises at least one blade having a length extending in a direction substantially perpendicular to a length of said at least one ferromagnetic strip.

58. The frame of claim 56 or any other preceding claim, wherein the at least one ferromagnetic strip further comprises a first strip and a second strip.

59. The frame of claim 58 or any other preceding claim, wherein a portion of the first strip is separated from a portion of the second strip by a gap.

60. The frame of claim 54 or any other preceding claim, further comprising at least one spacer that secures the first multi-pronged member to the third multi-pronged member and the second multi-pronged member to the fourth multi-pronged member.

61. The frame of claim 53 or any other preceding claim, wherein the first post, the first multi-pronged member, and the second multi-pronged member each comprise a ferromagnetic material.

62. The frame according to claim 54 or any preceding claim, wherein the second post, the third multi-pronged member, and the fourth multi-pronged member each comprise a ferromagnetic material.

63. The frame of claim 53 or any other preceding claim, wherein the first multi-pronged member includes a stem and two prongs coupled to the stem, wherein the two prongs are spaced apart from each other by a gap.

64. The frame of claim 63 or any other preceding claim, wherein each of the two prongs is curved.

65. The frame according to claim 54 or any other preceding claim, wherein the first multi-pronged member is disposed opposite the third multi-pronged member with a gap therebetween.

66. The frame of claim 65 or any other preceding claim, wherein the gap is an air gap.

67. The frame according to claim 65 or any other preceding claim, wherein the second multi-pronged member is disposed opposite the fourth multi-pronged member with a gap therebetween.

68. The frame of claim 54 or any other preceding claim, wherein the at least one permanent B ₀ The magnet is a biplane magnet comprising a first concentric permanent magnet ring and a second concentric permanent magnet ring.

69. The frame of claim 68 or any other preceding claim,

70. The frame of claim 68 or any other preceding claim,

71. The frame of claim 54 or any other preceding claim, further comprising a first plurality of ferromagnetic vanes.

72. The frame of claim 71 or any other preceding claim, wherein an end of each ferromagnetic leaf of the first plurality of ferromagnetic leaves is coupled with the first or third multi-pronged member.

73. The frame of claim 71 or any other preceding claim, wherein an end of each ferromagnetic leaf of the first plurality of ferromagnetic leaves is disposed within a slot formed within the first or third multi-pronged member.

74. The frame of claim 71 or any other preceding claim, wherein ferromagnetic vanes of the first plurality of ferromagnetic vanes are arranged to extend radially from a common center.

75. The frame of claim 71 or any other preceding claim, wherein the first plurality of ferromagnetic vanes comprises at least 16 vanes and at most 24 vanes.

76. The frame of claim 71 or any other preceding claim, wherein the first plurality of ferromagnetic vanes consists of between 10 and 30 vanes.

77. The frame of claim 71 or any other preceding claim, wherein each ferromagnetic vane of the first plurality of ferromagnetic vanes comprises silicon steel.

78. The frame of claim 71 or any other preceding claim, further comprising a second plurality of ferromagnetic vanes.

79. The frame of claim 78 or any other preceding claim, wherein an end of each ferromagnetic blade of the second plurality of ferromagnetic blades is coupled with the second or fourth multi-pronged member.

80. The frame of claim 71 or any other preceding claim, wherein each ferromagnetic blade of the first plurality of ferromagnetic blades is aligned to extend along a direction substantially parallel to one of an x-gradient magnetic field and a y-gradient magnetic field.

81. The frame of claim 80 or any other preceding claim, wherein the first plurality of ferromagnetic vanes consists of between 2 and 8 vanes.

82. The frame of claim 71 or any other preceding claim, wherein the first post and the second post are secured to each other by at least one bar, and wherein each ferromagnetic leaf of the first plurality of ferromagnetic leaves is aligned to extend in a direction substantially perpendicular to a length of the at least one bar.

83. The frame of claim 54 or any other preceding claim, wherein the first and second posts are arranged at an angle of 180 ° such that the at least one permanent B is ₀ A magnet is disposed between the first post and the second post.

84. The frame of claim 54 or any other preceding claim, wherein the first and second posts are arranged at an angle in a range from 100 ° to 180 °.

85. The frame of claim 54 or any other preceding claim, wherein the first and second posts are arranged at an angle in a range from 120 ° to 145 °.

86. The frame of claim 54 or any other preceding claim, further comprising at least one permanent magnet coupled with an inner surface of the first post.

87. The frame of claim 86 or any other preceding claim, wherein the at least one permanent magnet comprises at least one cylindrical permanent magnet.

88. The frame of claim 87 or any preceding claim, wherein the at least one permanent magnet comprises a first permanent magnet and a second permanent magnet, the first permanent magnet being disposed adjacent a first end of the first post and the second permanent magnet being disposed adjacent a second end of the first post.

89. The frame of claim 88 or any preceding claim, wherein the first permanent magnet has a first polarization and the second permanent magnet has a second polarization opposite the first polarization.

90. The frame according to claim 89 or any preceding claim, wherein one of the first polarization and the second polarization is directed towards an inner surface of the first post.

91. The frame of claim 87 or any preceding claim, further comprising at least one permanent magnet coupled to an inner surface of the second post.

92. The frame of claim 91 or any preceding claim, wherein the at least one permanent magnet coupled to the inner surface of the second post comprises a third permanent magnet and a fourth permanent magnet, the third permanent magnet disposed adjacent a third end of the second post and the fourth permanent magnet disposed adjacent a fourth end of the second post.

93. The frame of claim 92 or any preceding claim, wherein the third permanent magnet has a third polarization and the second permanent magnet has a fourth polarization opposite the third polarization.

94. The frame of claim 93 or any preceding claim, wherein one of the third polarization and the fourth polarization is directed towards an inner surface of the second post.

95. For providing B to MRI system ₀ An apparatus for magnetic fields, the apparatus comprising:

at least one permanentB ₀ Magnet to B of the MRI system ₀ The magnetic field contributes to the magnetic field; and

a ferromagnetic frame configured to capture and guide a magnetic field generated by B ₀ At least some of the magnetic fields generated by the magnets, the frame comprising:

a first plate configured to support at least one permanent B ₀ A magnet; and

a first post attached to the first plate using a first connection fitting, wherein the first connection fitting comprises:

a first connector connecting the first post with the first plate; and

a second connector attached to the first connector.

96. The apparatus of claim 95, the ferromagnetic frame further comprising:

a second post attached to the first plate using a second connector fitting, wherein the second connector fitting comprises:

a third connecting member connecting the second column with the first plate; and

a fourth connector attached to the third connector.

97. The device of claim 96 or any other preceding claim, wherein the ferromagnetic frame further comprises:

a second plate disposed opposite the first plate and configured to support the at least one permanent B ₀ A magnet, wherein:

the second plate is attached to the first post using a third connector fitting and to the second post using a fourth connector fitting, wherein:

the third connector assembly includes:

a fifth connector connecting the first post with the second plate; and

a sixth connector attached to the fifth connector; and

the fourth connector assembly includes:

a seventh connecting member connecting the second column with the second plate; and

an eighth connector attached to the seventh connector.

98. The apparatus of claim 95 or any other preceding claim, wherein the first connector comprises a ferromagnetic plate.

99. The apparatus of claim 98 or any other preceding claim, wherein the first connector comprises silicon steel.

100. The apparatus of claim 95 or any other preceding claim, wherein the first connector is secured to the first post and the first plate using a plurality of fasteners.

101. The apparatus of claim 95 or any other preceding claim, wherein the second connector is secured to the first post by a plurality of fasteners passing through the first connector.

102. The apparatus of claim 95 or any other preceding claim, further comprising at least one permanent magnet coupled with an inner surface of the first post.

103. The apparatus of claim 102 or any other preceding claim, wherein the at least one permanent magnet comprises a cylindrical permanent magnet.

104. The apparatus of claim 103 or any other preceding claim, wherein the at least one permanent magnet comprises first and second permanent magnets arranged along a length of the first post.

105. The apparatus of claim 104 or any other preceding claim, wherein the first permanent magnet has a first polarization and the second permanent magnet has a second polarization opposite the first polarization.

106. The apparatus of claim 105 or any other preceding claim, wherein one of the first polarization and the second polarization is directed toward an inner surface of the first pillar.

107. A magnetic resonance imaging system comprising:

the device of claim 95;

at least one radio frequency transmit coil; and

108. A method, comprising:

at least one permanent B ₀ Magnet for the MRI system B ₀ The magnetic field contributes to the magnetic field; and

a first plate configured to support the at least one permanent B ₀ A magnet; and

a first connector connecting the first post with the first plate; and

a second connector attached to the first connector.